A guide would be nice, but what you're asking for, is HVAC training.
Basically, a phase change system is composed of 4 parts:
-compressor
-evaporator
-condenser
-nozzle
Yes, having a res helps to make sure that the pump only compresses what it's supposed to compress is good, but otherwise, it only affects performance.
I found a source for refrigerants
here , but it is in the USA. You should check your local shops.